Amplifiers are commonly used in various electronic devices to provide signal amplification. Different types of amplifiers are available for different uses. For example, a wireless communication device (e.g., a cellular phone) may include a transmitter and a receiver for bi-directional communication. The receiver may use a low noise amplifier (LNA), while the transmitter may use a power amplifier (PA). In addition, the receiver and the transmitter may use variable gain amplifiers (VGAs).
Front-end circuit blocks may perform various functions such as filtering, switching between the transmitter and the receiver, impedance matching, and the like. These front-end circuit blocks may be implemented with discrete components external to an integrated circuit (IC) containing the low noise amplifier. Depending on the complexity of functions performed, these discrete, external components may substantially increase the cost and size of the receiver. Each of these circuit blocks may also exhibit insertion loss, which may degrade a noise figure (NF) of the receiver. Degrading the noise figure of the receiver degrades the performance of the receiver.
In an RF receiver, an input signal from the antenna first passes through the LNA that amplifies the input signal, while suppressing noise contributions. As a result, a low noise figure (NF) and high gain are important LNA performance parameters. In particular, LNA designs involve tradeoffs among linearity, input matching, power dissipation, and the like. These tradeoffs may dictate the type of LNA topology that is selected. For example, a common source (CS) LNA is a type of LNA that is popular due to its noise performance. Conversely, a common gate (CG) LNA is a type of LNA that provides a wideband input match that is less sensitive to input parasitic capacitance.